1. Sponsored by:
American Chemical Society, Campus Consortium for
Division of Chemical Health & Safety Environmental Excellence
http://www.dchas.org http://www.c2e2.org

2. Ralph Stuart, CIH
Environmental Safety Manager
University of Vermont

3. • Design History
• Open windows
• Laboratory furniture
• Pre-installed building equipment
• Integrated laboratory ventilation systems

4. • In the 1980’s, the rule of thumb was that
face velocities between 100 and 150 fpm
were the best indication of “safety”
• In the 1990’s, studies indicated that
measuring face velocity was not enough, so
tests using tracer gas were developed
(ASHRAE 110 testing)

5. • 1980’s: “It’s the labs’ problem”
• 1990’s: OSHA Lab Standard led to
Environmental Safety certification of face
velocity
• Around this time, maintenance workers
began to deal with hoods more systematically
• Upward exhaust
• Managing combined exhausts
• In the 2000’s, ASHRAE tracer gas testing of
containment “as installed” has become
common

6. • From an energy point of view, hoods are the
equivalent of a open window year round.
• Energy considerations focus on the volume of air moved
(air changes per hour) rather than its speed.
• Traditionally, facility managers have erred on the safety
side by over-ventilating laboratories
• As the number of hoods has proliferated and fuel
costs have risen, energy concerns have made
assessing “hood performance” more complicated
• Many ways of reducing the air volume exhausted have
been proposed.
• HVAC engineers now speak of “high performance” hoods
with regard to energy use, but (hopefully) without a
change in safety performance

7. • Laboratory buildings represent 15-20% of
campus floor space, but consume around 40%
of the campus’ energy
• Studies have found that only about 20% of the
installed hoods are used and someone is at
used hoods only 20% of that time.
• These observations lead to questions:
• Are chemical hoods and laboratory ventilation are the
best approach to laboratory safety?
• Do our laboratories really need to be open 24-7
with full HVAC services?
• Can we make assumptions about chemical risks
in the lab?

8. • Fume hoods were developed to control flammable
chemicals to control fires
• The chief reason for the popularity of fume hoods is that it is a
very adaptable design
• The design has been re-purposed to serve as containment
devices to protect human health from unclear potential risks
using the ALARA approach
• However, user behavior can trump design:
• To achieve ALARA, it’s important that lab workers follow good
hood work practices
• Proper use of a chemical hood requires a risk
assessment of the chemicals used so that the
protection strategy is clear.

9. • ANSI Standard Z9.5-2003
• Outlines a Laboratory Ventilation Management Program
with appointment of “responsible person” to oversee
laboratory ventilation systems.
• The general approach of the standard follows the
“management system” approach.
• This standard is referenced by many designers as well
as in the Labs-21 proposed LEED criteria

10. • Process Analysis
• Plan: Design
• Do: Use
• Check: Cost of operation
• Act: System maintenance
• Stakeholders
• Laboratory Designers
• Laboratory Workers
• Upper administration and
sustainability office
• Facility Operations and
Maintenance

11. • Laboratory Designers:
What hoods should we buy?
• Laboratory Workers:
When should I use hoods?
• Upper Management and Sustainability Office:
Do hoods have to cost so much?
• Campus Facility Managers:
How much money do I need to operate and
maintain hoods?

12. • External standards
• Fire Protection: NFPA 45
• Containment: ASHRAE 110
• Energy Use: LEED and Labs-21
• Possible design criteria
• Hoods must pass ASHRAE As Installed (0.1 ppm
leakage at 4 liters/minute); passing face velocity must
be established at installation
• Energy conservation in design: basis of design
documentmust describe design features (occupancy
sensors, sash sensors etc.) and be translated to users

13. • 40% workforce turnover every 2 years
• User signals and training:
1. Tell tales to determine if the hood is on
2. Warning signs in first 6 inches of hood
3. Safe Operating Height sticker
4. Close the sash reminder poster

14. • GHG impact: one chemical hood is the energy
equivalent of about 3 houses
• Each hood represents about $5000 to
$10,000/year in energy costs
• Laboratory buildings represent at least 35% of a
research campus’s energy use

15. • Hood maintenance needs:
• Face velocity check
• Calibration of alarms and controls
• Preventive maintenance of fans and hood
components
• Repairs
• System adjustments during renovations
• Re-commissioning and retro-commissioning
for proper hood performance, with regard to
both safety and energy

17. Robin M. Izzo
Associate Director
Princeton University
Environmental Health and Safety

18. • Effective at lower face
velocity
• Pass ASHRAE, EU tests
• Problems – design and
use
• Higher first costs
• Larger footprint

19. • Close sash when no one is
using the hood
• Princeton Step Pad Study:
time in front of hood = 5%
• Technology has improved
• Issues:
• Auto close vs. open
• Timing
• Proximity vs. motion

21. • Variable Air Volume is almost the standard
• Set back when unoccupied
• Timers
• Light switch
• Sash position
• Occupancy Sensors
• Higher first costs, quick payback
• Higher maintenance than Continuous air

23. • Especially useful with VAV systems
• Maximum number of hoods in use with sash
open at the same time
• Significant first cost savings
• Be realistic!!
• Always design n+1

24. • Teaching lab solution
• Three settings:
• On
• Off
• Set-up
• Lab instructor controls with key
• Princeton: per week
• on 15 hours, off 153 hours

25. • Not really fume hoods
• Limitations
• Filters
• Flow
• Code requirements
• Maintenance
• Limited application
• Gaining popularity
• Emerging technologies

26. • Old School: minimum 10-12 ACH (air
changes per hour) occupied
• New School: varies
• Computational Flow Dynamics Modeling
• Active Chemical Monitoring
• Some have gone to 4-8 ACH occupied or
lower based on these

27. • Know the applications
• Know the building
• Maintenance is key
• Still need a minimum airflow in the lab
• Limiting factor - USERS

28. • Very few regulations specifically about fume
hoods
• Many guidance documents
• International Mechanical Code 510
• Adopted by many municipalities
• 2006 version includes exemptions for labs
• Your mileage may vary

29. • Defines Hazardous Exhaust
• Precludes manifolding
• Requires sprinklering within the duct
• Requires detection within the duct
• MOST LAB APPLICATIONS fit under the
laboratory exemption
• Documentation is the key

30. • Work with your design team
• Talk to the users
• Understand the applications
• Look beyond those applications
• Try the options on for size
• Installation, visits, meetings
• There is no panacea – just because it works
for Princeton…

32. Sponsored by:
American Chemical Society, Campus Consortium for
Division of Chemical Health & Safety Environmental Excellence
http://www.dchas.org http://www.c2e2.org